Airborne onboard base transceiver station for mobile communication

Abstract

The invention refers to a base station (BTS) and a method for a BTS, for a cellular communication system comprising a user equipment (UE) onboard an aircraft, when at a predetermined altitude, and a terrestrial network. The invention is characterised in that the BTS is arranged to be an airborne onboard BTS comprising a screening device generating a first signal (S 1 ) matched to screen a second signal (S 2 ) from the terrestrial network at a predetermined altitude. The onboard BTS also comprises a signal generator generating a third signal (S 3 ) stronger than both the first signal (S 1 ) and the second signal (S 2 ), the onboard BTS arranged to establish a communication link with the UE via the third signal (S 3 ).

The invention claimed is: 
     
       1. A cellular communication system base station for use onboard an aircraft, the base station configured to communicate with a user equipment (UE) when the aircraft is at a predetermined altitude, the UE nominally configured to communicate with a terrestrial network, said base station comprising:
 a screening device operative to generate a first signal matched to screen a second signal from a terrestrial network when at said predetermined altitude; and, 
 a signal generator operative to generate a third signal stronger than both the first signal and the second signal, the base station operative to establish a communication link with the UE via the third signal; 
 wherein the first signal has a signal strength less than the signal strength of the second signal but not lower than a predetermined value below the signal strength of the second signal, whereby a noise ratio for the UE is not acceptable for homing in on a certain frequency within a frequency band of the second signal such that the UE cannot establish a communication link to the terrestrial network via the second signal; 
 wherein the third signal is generated with a signal strength stronger than the first signal and at a certain frequency or frequencies and having an acceptable signal to noise ratio of at least 7 dB for the UE such that the UE can home in on the third signal in order for the onboard base station to establish said communication link with the UE; 
 wherein the screening device is operative to generate the first signal in the form of a pulsed first signal matched to screen a control channel in the second signal; and, 
 wherein the screening device is operative to generate the pulsed first signal with a pulse length at least of a same length as the pulse length of the control channel and with a repetition interval less than a broadcast channel burst length. 
 
     
     
       2. A base station according to  claim 1 , wherein the third signal has a third frequency band being at least partly or completely within a first frequency band of the first signal. 
     
     
       3. A base station according to  claim 2 , wherein the first frequency band is equal to or greater than a second frequency band of the second signal. 
     
     
       4. A base station according to  claim 1 , wherein the first signal has a first effect being matched to screen the second signal having a second effect, and where the third signal has a third effect being greater than the first effect and/or the second effect. 
     
     
       5. A base station according to  claim 1 , the communication system pertaining to a (Global System for Mobile communication) GSM cellular communication system, wherein the screening device is arranged to generate the pulsed first signal with a pulse length being at least 4.616 ms and with a repetition interval not exceeding 23.5 ms. 
     
     
       6. A base station according to  claim 1 , wherein the base station is connected to an onboard antenna. 
     
     
       7. A base station according to  claim 6 , wherein the onboard antenna is in the form of a leaky cable extending in a longitudinal direction of the aircraft and in the vicinity of a passenger using a UE. 
     
     
       8. A base station according to  claim 1 , wherein the base station is connected to a satellite link for traffic between the base station and a dedicated base station in the terrestrial network. 
     
     
       9. A base station according to  claim 8 , wherein the satellite link comprises an onboard satellite antenna arranged to send signals to a satellite positioned at a higher level than the aircraft. 
     
     
       10. A cellular communication system base station for use onboard an aircraft, the base station configured to communicate with a user equipment (UE) when the aircraft is at a predetermined altitude, the UE nominally configured to communicate with a terrestrial network, said base station comprising:
 a screening device operative to generate a first signal matched to screen a second signal from the terrestrial network when at a predetermined altitude; and, 
 a signal generator operative to generate a third signal stronger than both the first signal and the second signal, the base station operative to establish a communication link with the UE via the third signal; 
 wherein the screening device is operative to generate the first signal in the form of a pulsed first signal matched to screen a control channel in the second signal, said pulsed first signal having a pulse length at least of a same length as the pulse length of the control channel and with a repetition interval less than a broadcast channel burst length; and, 
 wherein the communication system is a (Global System for Mobile communication) GSM cellular communication system, wherein the screening device is operative to generate the pulsed first signal with a pulse length of at least 4.616 ms and with a repetition interval not exceeding 23.5 ms. 
 
     
     
       11. A method in a cellular communication system base station for use onboard an aircraft, the base station configured to communicate with a user equipment (UE) when at a predetermined altitude, the UE nominally configured to communicate with a terrestrial network, the base station comprising a screening device and a signal generator, said method comprising:
 generating, using said screening device, a first signal matched to screen a second signal from the terrestrial network at a predetermined altitude; 
 generating, using said signal generator, a third signal stronger than both the first signal and the second signal, the base station operative to establish a communication link with the UE via the third signal; 
 wherein the first signal has a signal strength less than the signal strength of the second signal but not lower than a predetermined value below the signal strength of the second signal, whereby a signal to noise ratio for the UE is not acceptable for homing in on a certain frequency within a frequency band of the second signal such that the UE cannot establish a communication link to the terrestrial network via the second signal; 
 wherein the third signal is generated with a signal strength stronger than the first signal and at a certain frequency or frequencies and having an acceptable signal to noise ratio of at least 7 dB for the UE such that the UE can home in on the third signal in order for the base station to establish a communication link with the UE via the third signal; 
 wherein the screening device is operative to generate the first signal in the form of a pulsed first signal matched to screen a control channel in the second signal; and, 
 wherein the screening device is operative to generate the pulsed first signal with a pulse length at least of a same length as the pulse length of the control channel and with a repetition interval less than a broadcast channel burst length. 
 
     
     
       12. A method in a cellular communication system base station for use onboard an aircraft, the base station configured to communicate with a user equipment (UE) when at a predetermined altitude, the UE nominally configured to communicate with a terrestrial network, wherein the base station comprises a screening device and a signal generator, said method comprising:
 generating, using said screening device, a first signal matched to screen a second signal from the terrestrial network at a predetermined altitude; and, 
 generating, using said signal generator, a third signal stronger than both the first signal and the second signal, the base station operative to establish a communication link with the UE via the third signal; 
 wherein the screening device is operative to generate the first signal in the form of a pulsed first signal matched to screen a control channel in the second signal; 
 wherein the screening device is operative to generate the pulsed first signal with a pulse length at least of a same length as the pulse length of the control channel and with a repetition interval less than a broadcast channel burst length; and, 
 wherein the communication system is a (Global System for Mobile communication) GSM cellular communication system, wherein the screening device is operative to generate the pulsed first signal with a pulse length at least 4.616 ms and with a repetition interval-not exceeding 23.5 ms. 
 
     
     
       13. The cellular communication system base station recited in  claim 1 , wherein said predetermined value is 6.5 dB. 
     
     
       14. The cellular communication system base station recited in  claim 1 , wherein said predetermined value is 7.0 dB. 
     
     
       15. The method in a cellular communication system base station recited in  claim 11 , wherein said predetermined value is 6.5 dB. 
     
     
       16. The method in a cellular communication system base station recited in  claim 11 , wherein said predetermined value is 7.0 dB. 
     
     
       17. The method in a cellular communication system base station recited in  claim 11 , wherein the third signal has a third frequency band being at least partly or completely within a first frequency band of the first signal. 
     
     
       18. The method in a cellular communication system base station recited in  claim 17 , wherein the first frequency band is equal to or greater than a second frequency band of the second signal. 
     
     
       19. The method in a cellular communication system base station recited in  claim 1 , wherein the first signal has a first effect being matched to screen the second signal having a second effect, and where the third signal has a third effect being greater than the first effect and/or the second effect. 
     
     
       20. The method in a cellular communication system base station recited in  claim 1 , the communication system pertaining to a GSM cellular communication system, wherein the screening device is arranged to generate the pulsed first signal with a pulse length being at least 4.616 ms and with a repetition interval not exceeding 23.5 ms. 
     
     
       21. The method in a cellular communication system base station recited in  claim 1 , wherein the base station is connected to an onboard antenna. 
     
     
       22. The method in a cellular communication system base station recited in  claim 21 , wherein the onboard antenna is in the form of a leaky cable extending in the longitudinal direction of the aircraft and in the vicinity of a passenger using a UE. 
     
     
       23. The method in a cellular communication system base station recited in  claim 1 , wherein the base station is connected to a satellite link for traffic between the base station and a dedicated base station in the terrestrial network. 
     
     
       24. The method in a cellular communication system base station recited in  claim 23 , wherein the satellite link comprises an onboard satellite antenna arranged to send signals to a satellite positioned at a higher level than the aircraft.